The present invention relates to the electronics field of solid-state electrical measurement apparatus. More particularly, the present invention relates to solid-state electrical meters having light-emissive displays and floating electrical inputs.
Electrical meters of the electromechanical type (such as the D'Arsonval type) are well known, but such meters frequently exhibit disadvantageous large size, incompatibility with direct printed circuit mounting and soldering, lack of self-emitting displays, and substantial per-unit cost. Galvanometers of the electromechanical type frequently exhibit the same disadvantages, but the designer's desire for their additional advantage of reading both electrical polarities on the same scale is often offset by considerations of even higher per-unit cost and occasional out-of-stock unavailability problems. Also, even the least expensive electromechanical meters may feature a much higher accuracy than the designer needs for a given low-accuracy application.
Recently, light-emitting meters using light-emitting diodes or neon light emitters for displays have been offered in an apparent attempt to compete with other meters in a relatively high-accuracy end of the meter market. However, none of these apparently are price-competitive with the least expensive lower-accuracy electromechanical meters at the low end of the market. Moreover, light-emitting meters are likely to be powered by a power supply having a ground. This presents a problem of how a radically simplified light-emitting meter might be constructed with floating input terminals, that is, terminals neither of which are significantly constrained in their voltage relationship to that ground.